Method for scouring and dyeing silk in a single operation

ABSTRACT

THE SILK IS SKEIN, THREAD OF FABRIC SHAPE IS TREATED IN A SINGLE OPERATION INSIDE A SINGLE BATH WITH DEGUMMING REAGENTS AND WITH DYESTUFFS. TO THIS END, THE SILK IS SOAKED IN AN AQUEOUS BATH CONTAINING A TENSION-ACTIVE REAGENT AND WITH WHICH THE DEGUMMING REAGENT AND DYESTUFFS ARE INCORPORATED IN SEQUENCE WITH INTERMEDIATE STIRRING PERIODS PROVIDED BY A CIRCULATION OF THE BATH OVER THE SILK. THE PH OF THE BATH IS CAUSED TO DROP SHARPLY THROUGH ADDITION OF SULFURIC ACID FOR INSTANCE FROM 9 TO 10 DOWN TO 5 OR EVEN 6 TO 6.5. THIS PROCEDURE REDUCES THE HANDLING OF THE SILK TO A MINIMUM.   D R A W I N G

Man-ch20. 1913 M H AL 3,121,522

METHOD FOR SCOURING AND DYEING SILK IN A SINGLE OPERATION Filed Nov. 4, 1959 2 Sheets-Sheet l 1h05' 1h20' 1h35' 1h'50 2h0 Temps I MQICLZO, 1973 MACHQN ETAL 3,721,522

METHOD FOR SCOURING AND DYEING SILK IN A SINGLE oPEh TIoN Filed Nov. 4. 1969 :2 Sheets-Sheet 2 United States Patent Oifice 3,721,522 Patented Mar. 20, 1973 US. Cl. 8-19 10 Claims ABSTRACT OF THE DISCLOSURE The silk in skein, thread or fabric shape is treated in a single operation inside a single bath with degumming reagents and with dyestuffs. To this end, the silk is soaked in an aqueous bath containing a tension-active reagent and with which the degumming reagent and dyestuffs are incorporated in sequence with intermediate stirring periods provided by a circulation of the bath over the silk. The pH of the bath is caused to drop sharply through addition of sulfuric acid for instance from 9 to 10 down to or even 6 to 6.5. This procedure reduces the handling of the silk to a minimum.

Our invention has for its object a method for scouring and simultaneously dyeing natural silk. Our invention relates more particularly to the technical treatment and dyeing of such textile material.

There are chiefly two operative steps during the preparation of natural silk, to wit: the scouring or degumming, that is the removal of the sericine or silk gum whereas the fibroin should not be damaged, which scouring is followed by the dyeing. Said successive operative steps are generally executed conventionally in sequence and this leads to numerous handlings and consequently to an increase in the staff required and in the cost price. The cost of production is substantially higher considering that silk is an expensive and delicate product which is readily damaged during such handlings.

Now, our invention is of particular interest since our improved method cuts out these drawbacks and leads to substantial advantages which will appear upon reading of the following description.

The chief feature of our invention consists in that the removal of the gum through scouring and the dyeing are executed as a single operation within a single bath of which the pH is controlled very carefully during the different stages of the treatment, said control being obtained through incorporation with the bath of reagents under predetermined conditions governing the transfer and fixing of the dyestuff molecules on the fibroin after removal of the sericine. Said transfer is chiefly furthered by a speedy and sudden modification of the pH and by the relative movement of the bath with reference to the silk material; various modifications may in fact be made in carrying out the method according to whether the natural silk is treated as threads in skein shape or else as wound over perforated tubes or cones or else on sleeves or again as woven, knitted or braided pieces of fabric.

According to a further feature of our invention, the scouring reagents are preferably, but not necessarily constituted by tertiary, quaternary or the like salts of ammonium or else by soaps containing no tannin.

Said advantages and features will appear together with other features and advantages from the reading of the following description. In order to properly define the object of our invention without limiting however its scope,

reference is made to the accompanying drawings illustrating preferred embodiments of our invention.

FIG. 1 is a graph illustrating the method and showing the modifications in the pH during the treatment with reference to time.

FIGS. 2 to 4 are predominantly diagrammatic views illustrating various apparatus adapted for the execution of our improved treatment according to the shape assumed by the natural silk whether a skein, a fabric or a reel carried by a sleeve, cone, tube or the like.

FIG. 5 is a cross-section through line 55 of FIG. 4.

FIG. 6 is a cross-section of a bayonet fitting for reels or cones.

We will now describe our improved method in such various modifications governed by the shape assumed by the natural silk; there is shown by Way of example in FIG. 2 a machine carrying perforated reels of a known type used for treating according to our improved method skeins E of natural silk. Said machine includes a vat 1, pipes 2 leading upwardly out of the vat towards hollow skein-carrying arms or reels 3 extending over the bath in the vat. Said arms are closed at their free ends and perforated along their upper generating lines as shown at 311 to allow the treating liquid passing out of the bath into said arms to flow out of the latter. A pump 4 controls the circuit of the liquid between the bath in the vat and the arms or reels 3. The machine is furthermore equipped with any conventional means for heating the bath, which means are not illustrated.

The silk is treated in the vat by means of a bath the volume of which is approximately in the proportion of 30 litres of the bath for each kg. of silk to be treated.

Said bath is constituted chiefly by fresh or softened water incorporating a tensio-active reagent, that is a wetting product of the type usually sold in trade under different registered trademarks. About 0.5 gr. of said tensio-active product should be used for each litre of bath.

The bath being poured into the vat, the procedure is as follows:

The bath is heated up to about 35 C. and the natural silk forming skeins E is wetted for about 10' min. during which the pump 4 is operative.

The pump being stopped, the bath is heated to about C.

The degumming product is fed into the bath, said product being a tertiary, quaternary or the like ammonium salt or else a soap containing no tannin. This product should be used in amounts corresponding very approximately to about 6% by weight of the silk to be treated. The incorporation of said product with the bath is obtained at the origin of times shown in abscissae on the graph of FIG. 1. At said point 0, the pH of the bath is of a magnitude of 9.5 to 10.

The pump or pumps being started again, the bath is caused to circulate during about 5 min. at an approximate temperature of 92 C.

The pump or pumps are stopped again and the dyestuff or dyestuffs are added to the bath. All usual types of dyestuffs are consistent with the treatment and suitable in this case. Said dyestuffs are used in amounts and ratios of a conventional value and incorporated in order to obtain the desired result independently of the objects of our improved method. It is therefore not necessary to go into any detail as to said incorporation of such known dyestuffs.

The pump or pumps are started again so as to cause the bath to circulate with the dyestuffs carried by it at a temperature of about 92 C. The addition of dyestuffs is accompanied by a reduction in the value of the pH approximately as illustrated in the graph of FIG. 1.

3 The value of the pH of the bath is checked about 20 min. after the beginning of the procedure by means of a pH meter or of any known and suitable means. According to the result of this checking there is then introduced the required amount of sulfuric acid H 80 or the like,

, so as to obtain a pH the value of which ranges between 6 and 6.5 as illustrated in ordinates in the graph of FIG. 1. This furthers the adherence and action of the dyestuff on the fibroin. The speedy and sharp modification of the pH sinking from a value of about 9 to 9.5 to about 6 to 6.5 stops the degumming operation.

The action of the dyestuffs and dyeing step continues during 30 min. or thereabouts or even up to about 50 min. as shown on the scale of times of the graph of FIG. 1.

During this last period, the action of the bath is checked through examination of one or more samples of the silk and there is optionally added, if required and in accordance with the observations made, one or more dyestuffs and/or sodium sulfate Na SO whose function is wellknown in the dyeing industry and consists in increasing and marking more strongly the intensity of the color by furthering the setting on the fibroin of the non-fixed dyestuif still remaining in the bath. These different additions are accompanied according to their importance and as shown in the graph of FIG. 1 by a rise in the value of the pH.

The procedure is allowed to continue until the moment elapsed since the beginning of the operation reaches 1 /2 to 2 hours, said procedure being brought to an end in a conventional manner by emptying the vat 1. The dyed skeins E are then rinsed and the usual finishing treatment is executed in accordance with conventional practice.

When the natural silk is to be treated after it has been woven, knitted or braided, it is necessary to resort for in-' stance to a machine of the type illustrated diagrammati cally in FIG. 3. Said machine includes a vat in which an endless chain constituted by transverse bars 7 is caused to progress continuously under the action of any suitable means such as the wheels 6. Means for heating the bath are also provided. The piece P of woven, knitted or braided natural silk wound off a roll R passes through the bath in the vat and is wound again over the roll R1, for instance by means of compressing and driving cylin-' ders 8.

The liquid forming the bath is then transferred in accordance with a continuous cycle by means of a pump 9 through a channel 10 starting from the lower section of the vat 5 up to a trough 11 feeding it back into the vat. The trough extends throughout the breadth of the bath 7, of the chain bars 7 and of the fabric P at the very point of introduction of the fabric into the bath.

Consequently, the liquid forming the bath drops onto the fabric P between the two bars 7 and thus produces a vertical sliding movement of said fabric between the bars 7 so as to form loops P1.

In this embodiment, the bath is prepared again as described hereina bove and the treating procedure is the same as in the case described with reference to FIG. 2, the dyestutf being incorporated with the bath slightly after the degumming product.

However, depending on the structure of the piece of silk P, the drop in pH through addition of sulfuric acid or the like is less considerable than in the preceding case and it may pass from about 9 to 9.5 to a value approximating 7.5.

Generally when the percentage of dyestutf to be added with a view to obtaining the required hue has been correctly calculated the dyeing and degumming are finished simultaneously. This cuts out the additional incorporations of a dyestulf and/or sodium sulfate.

Lastly, within the scope of our invention as defined in the accompanying claims, the method may also be executed when the natural silk is constituted by threads wound over perforated sleeves, reels, tubes or cones as illustrated at B.

There is used in such a case a machine of a conventional type such as that illustrated by way of example in FIGS. 4 and 5. Said machine includes a vat 12 which may be closed fluidtightly by a cover 12a. Over the bottom of the vat there is laid a hollow plate 13 out of which tubes 14 rise vertically which tubes are provided with multiple perforations. Said tubes are closed at their upper ends which assume a tapering shape in order to further the fitting of the reels B threaded over the tubes.

The plate 13 and tubes 14 may be fitted removably in the vat which furthers and accelerates the fitting and subsequent removal of the reels.

A channel 15 connects the bottom of the vat with the inside of the hollow plate 13. One or more pumps 16 provide for the circulation of the liquid of the bath which passes inside the plate 13 and thence into the tubes 14 so as to enter the perforated reels B and the silk wound round said reels, after which the liquid is recycled. A system for heating the bath is provided. Instead of perforated tubes 14, it is also possible to resort to a bayonet support over which are fitted reels or cones carrying the silk threads as shown cross-sectionally in FIG. 6.

For the degumming and dyeing of the silk in reel or the like formation it is again possible to resort to a bath prepared under the conditions already disclosed for the treatment of silk in skein formation.

However in such a case it is necessary to take into account the fact that the incorporation of the degumming product with the bath obviously leads to a substantial elimination of the sericine (about 25% of the original weight). This results in that the reels or cones B are no longer homogeneous. The silk wound round them assumes a slack consistency and this leads to the formation of preferential passageways for the liquid of the bath, while the degumming is imperfect and irregular and consequently the dyeing would be of a poor grade.

In order to cut out this drawback the invention provides means for giving the silk, after the introduction into the bath of the degumming reagent, a physical shock as soon as the swelling of the sericine begins, with a view to removing said sericine. Such a shock is obtained by stopping the circulating pump or pumps 16 acting on the bath as soon as the vat 12 is filled with the liquid forming the bath, which liquid is brought to a temperature of about C. while the chemical reaction is initiated between the degumming reagent, such as an ammonium salt or a soap without any tannin and the sericine.

The circulation of the bath should necessarily be stopped as soon as the vat is full and in any case as soon as the sericine has begun swelling and before the swelling has been brought to completion. The duration of this complete swelling is readily ascertained since it depends on the ratio between the weight of the degumming reagent and the volume of the bath.

It is thus possible to prevent the formation of preferential passageways within the bulk of the silk wound round the reels B since the liquid bath had circulated and had been distributed throughout the windings of the reels before the stopping of the pumps and even the complete filling of the vat.

The pump or pumps 16 are started again after the rest period has lasted about 15 mins. and the physical shock is thus obtained at this moment. The degumming is consequently operated in a homogeneous and uniform manner throughout the silk material. This can be checked by the uniform flow assumed by the liquid forming the bath. Consequently, the dyestuff is fixed in a perfectly homogeneous and uniform manner throughout the silk round the sleeves, tubes or cones.

After the physical shock obtained in the manner described, a further operative step is executed so as to bring the degumming to a finish by adding the dyestuff while heating the bath to about 104 C. The further operative steps are those precedingly described including chiefly a speedy and sudden modification of the pH.

The interest and advantages of the method according to our invention and the various manners of executing it have thus been fully disclosed.

It should be remarked more particularly that the treatment is extremely simple and the staff required for the execution of the method is reduced, While the substantial lowering of the cost price of production, the high grade of homogeneity of the treated material and in particular of the dye obtained form considerable advantages of the invention.

Our invention is by no means limited to the embodiments disclosed and to the arrangement of the different parts of the machine referred to hereinabove and it covers in contradistinction all the modifications lying within the scope of the accompanying claims.

What we claim is:

1. A method for simultaneously degumming and dyeing natural silk comprising immersing the silk in a bath of pure water containing surface-active agent, adding to said bath a degumming reagent to obtain a pH of from 9 to 10, stirring the bath, adding to said same bath at least one dyestuff, stirring the bath until about 20 minutes has elapsed from the time the degumming agent was added, adding suflicient acid to cause the pH to drop suddenly by at least 1.5 points and removing the silk out of the bath when dyed to the desired shade.

2. A method as claimed in claim 1 according to which the volume of the bath measured in litres is about 30 times the figure in 'kgs. measuring the weight of the silk undergoing treatment inside said bath and the weight of the surface-active agent added to said bath is eqal to about 0.5 gr. for each litre of water.

3. A method as claimed in claim 1 wherein the degumming reagent is constituted by an ammonium salt.

4. A method as claimed in claim 1 wherein the degumming reagent is a tannin-free soap.

5. A method as claimed in claim 1 applied to silk skeins according to which the skeins are soaked for about 10 mins. in the bath raised at about 35 C. before the addition of the degumming reagent and the bath is then heated to about 95 C. after stirring before said addition of the degumming reagent, said degumming reagent being added in a proportion of about 6% by Weight with reference to the silk undergoing treatment in the bath and the temperature being maintained at about 92 C. during the addition of the dyestuff.

6. A method as claimed in claim 1 applied to silk skeins according to which the skeins are soaked for about 10 mins. in the bath raised at about 95 C. before the addition of the degumming reagent and the bath is heated to about C. after stirring before said addition, said degumming reagent being added in a proportion of about 6% by weight With reference to the silk undergoing treatment in the bath and the temperature being maintained at about 92 C. during the addition of the dyestulf and the drop in pH lowering it down to about 6 to 6.5 by addition of a strong acid.

7. A method as claimed in claim 1 according to which the bath is drained after the dyeing step, and the silk is rinsed.

8. A method as claimed in claim 1 applied to pieces of silk fabric according to which the drop in pH lowers it down to about 7.5, the dyeing and degumming steps ending substantially at the same moment.

9. A method as claimed in claim 1 applied to silk threads wound over perforated carriers according to which the bath is raised to about 95 C. after addition of the degumming reagent and the bath remains unstirred for about 15 mins., starting from the moment at which the degum ming reagent has begun its action by initiating a swelling of the sericine of the silk, to ensure a uniform degumming.

10. A method as claimed in claim 1 applied to silk threads wound over perforated carriers according to which the bath is raised to about 95 C. after addition of the degumming reagent and the bath remains unstirred for about 15 mins. starting from the moment at which the degumming reagent has begun its action by initiating a swelling of the sericine of the silk, to ensure a uniform degumming, the bath being raised to about 104 C. during the dyeing step to ensure a further degumming.

References Cited UNITED STATES PATENTS 836,464 11/1906 Schmid 8-19 1,446,860 2/1923 Seyer 819 X 2,169,881 8/1939 Mosher 819 1,446,834 2/1933 Cole 819 X FOREIGN PATENTS 301,419 8/1929 Great Britain 8-138 OTHER REFERENCES Knecht: Manual of Dyeing, pp. -156, vol. 1, 9th edition, pub. by Mapleton House, Brooklyn, NY.

Knecht: A Manual of Dyeing, Pub. 1945, p. 67, pub. by Mapleton House, Brooklyn, NY.

DONALD LEVY, Primary Examiner 

